This invention relates to a method for determining the operating state of an energy-storage battery in assumed temperature and state of charge conditions.
DE 37 12 629 C2 describes a measurement apparatus for the remaining life of a motor vehicle battery which detects battery voltage and associated load current value before and after initial starting with the battery in the fully charged state. It determines the temperature-compensated internal resistance and stores this in a memory, and compares it with internal resistance values determined during the subsequent processes of starting the internal combustion engine. The remaining life is then indicated as a function of predetermined, stored threshold values.
A vehicle battery operating state monitor is known from EP 0 438 477 B1 (De 689 24 169 T2). A vehicle battery is monitored to determine the battery capacity, state of charge and specific fault states. The ambient temperature, battery voltage, generator/regulator output voltage and currents in and out of the battery are measured continuously. Current/voltage data is analyzed to determine the internal resistance and polarization of the battery. Furthermore, an investigation is carried out with regard to the state of charge and fault states which result from corroded connecting terminals and a low electrolyte level. The cold start limit is determined by comparing the possible power output of the vehicle battery with the power required by the vehicle for the starting process. Data produced by the comparison is indicated on the vehicle dashboard.
An electronic tester fro assessing the capacity of a battery or cell is disclosed in EP 0 548 266 B1 (DE 691 31 276 T2). An independent electronic circuit provides an instantaneous assessment of the energy storage capacity of individual two-volt lead-acid cells or batteries which are composed of such cells. The tester is electrically connected to the connections of a cell or battery and measures the dynamic conductivity using a small signal that varies with time. An internal standard conductivity allows calibration of the tester to ensure the accuracy of the cell/battery measurements. Auxiliary terminals offer the capability for connection of a xe2x80x9creference conductivityxe2x80x9d, which is defined as the dynamic conductivity of an identically designed and produced cell or battery with 100% energy storage. The tester indicates either the conductivity of the tested cell/battery in Siemens (mhos) or its xe2x80x9cpercentage capacityxe2x80x9d determined by normalization of the measured conductivity with respect to the xe2x80x9creference conductivityxe2x80x9d. When the xe2x80x9cpercentage capacityxe2x80x9d is determined, a light-emitting diode illuminates when the result is below a preset limit value. When using individual cells, specific apparatus prevent high-current elements of the measurement circuit being fed directly by the two-volt cell under test by supplying these elements with low current, but with a higher voltage from a separate low-energy direct-current source, for example a small 9 volt transistor battery or a permanently installed DC/DC voltage converter, which is fed by the cell under test. This circuit design allows a transportable, independent electronic instrument, allowing the xe2x80x9cpercentage capacityxe2x80x9d of a two-voltage cell or a battery which is composed of such cells to be assessed exactly on an instantaneous basis without any additional external power supply.
DE 197 50 309 A1 relates to a method for determining the starting capability of a starter battery of a motor vehicle in which the mean value of the voltage drop on starting the internal combustion engine is measured and compared with the voltage values of a family of characteristics, with the family of characteristics being based on measured voltage drops and associated battery and engine temperatures. In the method, the discrepancy between the instantaneously determined voltage drop and the voltage drop stored in the family of characteristics is determined, and an indication and alarm function is initiated as soon as the discrepancy exceeds a predetermined threshold value.
The conventional methods allow the actual state of an energy-storage battery to be evaluated and the internal resistance to be determined for the actual battery temperature and the actual state of charge. However, it is quite difficult to use this to predict the operating state under the influence of the operating age of the energy-storage battery for any desired further assumed temperature and state of charge conditions.
It would therefore be advantageous to provide a method for determining the operating state of an energy-storage battery in which the operating state can be predicted reliably for a desired further assumed temperature and state of charge conditions in assumed temperature and state of charge conditions by simple measurement of a temperature variable which is correlated with the battery temperature, determination of the state of charge and of a further state variable for the energy-storage battery.
This invention relates to a method for determining the operating state of an energy-storage battery in assumed temperature and state of charge conditions including measuring a temperature variable (TACT) which is correlated with a battery temperature (TBAT), determining a state of charge (SOCACT) of the energy-storage battery, and determining a further state variable (AACT) of the energy-storage battery, forming a reference value (BV) from a reference between the further state variable (AACT) and a corresponding state variable (ANEW) of a substantially identical, new energy-storage battery with the same temperature variable (TACT) and the same state of charge (SOCACT), and determining a predicted state variable (AP) as a measure of operating state for an assumed temperature variable (TP) and an assumed state of charge (SOCP) from known comparison reference values (BT), which have been recorded as a function of temperature variables (T), states of charge (SOC) and the aging state of identical energy-storage batteries.